Devices for testing the blood and breath alcohol content of a human subject have been used for many years. This type of testing is typically done using breath alcohol testing methods, for example, see U.S. Pat. No. 3,940,251, entitled "Apparatus for Detecting or Measuring a Constituent of a Gas", issued Feb. 24, 1976 to Jones, et al. This system tests the alcohol content of a subject's breath by utilizing a breath analyzing sensor in a breath sampling system that includes a disposable tube. A subject exhales into the tube and an operator of the handheld instrument pushes a button releasing a spring loaded pump which draws a deep lung breath sample into the device. The breath sample is then analyzed by a sensor and the subsequent reading is interpreted by the operator.
More recently such breath alcohol testing instruments have been added to Home Arrest Systems. These systems have an encoded transmitter and a base receiver unit. The transmitter is attached to the subject, and the system determines if the subject is located within a short distance, usually under 250 feet, from the base receiver unit. These systems may attach a conventional breath alcohol testing device to the base unit.
Other prior art, for example U.S. Pat. No. 4,843,377 issued Jun. 27, 1989 to Fuller et al., and U.S. Pat. No. 4,916,435 issued Apr. 10, 1990 to Fuller, consists of a one way video system with an attached conventional breath alcohol tester. This system transmits a picture of the test results, along with a picture of the subject taking the test, over conventional phone lines to a central monitoring station. An operator at the central station must view the video picture to help assure that the proper subject is taking the breath alcohol test. U.S. Pat. No. 4,665,385 entitled "Hazardous Condition Monitoring System", issued May 12, 1987 to Henderson consists of a hazardous gas sensor and an ethanol sensor located near a microphone attached to a walkie talkie. The system transmits encoded information pertaining to hazardous gas levels and subject breath alcohol levels when the walkie talkie is used.
U.S. Pat. No. 4,997,770 entitled "Method and Means for Detecting Blood Alcohol in Humans by Testing Vapor above the Eye", issued Mar. 5, 1991 to Giles, et al., measures the blood alcohol content of vapors emitted by the human eye. This device requires that a cup be placed over the subject's eye, and a separate analyzer measures the alcohol content of gases collected in the cup.
All the prior art described above requires the full cooperation of the subject to complete a successful breath test. Except for the system of Henderson, none of the remote alcohol systems described above are portable. Also, except for Giles et al., all the prior art described above measures breath alcohol content.
Alcohol monitoring systems are currently needed to periodically measure a subject's blood alcohol level at a remote location over an extended period of time, such as when a subject is in an alcohol rehabilitation program, or is under court order to not consume alcohol. For this type of system, identification of the subject providing the breath sample is a very significant problem. For example, an unsupervised remote breath alcohol tester being used by the subject is ineffective if an operator is not available to identify that the correct subject is breathing into the instrument. Because of the requirement of subject identification, these systems typically require the active participation and cooperation of the subject. Sometimes the subjects are uncooperative and will go to great lengths to avoid the testing. This increases the time and effort necessary to perform the testing, which often results in less testing being performed.
Another problem is that once a subject has been tested, the subject knows they will not be tested again for some period of time, such as when the subject is involved in a work release or outpatient alcohol rehabilitation program. This allows the subject to leave the location of the stationary remote alcohol breath tester unit and immediately consume alcohol at high levels just after the testing. The subject is unlikely to show a high level of alcohol content if tested at a much later time because the rate of dissipation of alcohol from the human body is quite high.
Another major problem of all of these systems is the lack of any effective means to determine if a positive reading is created by ethanol in the testing subject's breath or blood, or by tampering with the instrument, such as, by pouring alcohol over the sensor in an effort to discredit the instrument. A wide variety of common interferant gases will react with the sensors utilized in the systems in a manner very similar to ethanol, which may provide a false positive reading and it is important to be able to screen out interferant gases. For a subject in an alcohol treatment program, a false reading may have severe consequences.
There is need in the art then for an apparatus and method to passively test the blood alcohol content of a human subject. There is further need for such a system to passively confirm the identity of the subject during such testing. Still another need in the art is for such a system to perform such testing automatically without the need of an operator, and without the need for cooperation from the subject being tested. A further need in the art is for such a system to perform frequent testing at either predetermined times, or at random times, and to perform such testing at any arbitrary location Another important need unanswered by prior art is a means of determining if a reading indicating the subject has consumed alcohol is caused by the blood alcohol levels of the subject or by numerous interferant gases which react with sensors in a manner similar to alcohol The present invention satisfies these and other needs.